The invention disclosed herein pertains to a system wherein hot water is dispensed from a faucet substantially coincidentally with opening of the faucet.
Systems for heating and dispensing hot water instantly are basically known. "Hot" as the term is used in this case means water at a temperature of about 190.degree. F. (88.degree. C.) or slightly higher but always below the boiling point. Water at this high temperature is usually made available at a dedicated faucet for individuals who need hot water to make instant coffee, tea or cocoa, for example. A typical preexisting system heats water in a relatively small capacity tank which is situated below the sink on which the faucet is mounted. The tank may have a capacity of 1/3 or 1/2 gallons (1.3 or 1.9 liters). The tank is divided into two chambers, a main chamber in which water is heated electrically and an expansion chamber that is contiguous with the main chamber and into which water being heated in the main chamber is allowed to expand. The tank is vented to the atmosphere to preclude build up of pressure in the tank which is necessary because the tank usually has a thin wall which may even be a plastic material instead of metal.
Every time hot water is drawn from the tank, due to opening of the faucet, it is necessary to withdraw the hot water from the expansion chamber of the tank to provide for expansion of the replenishment cold water that is supplied to the main tank chamber from the building water system. Cold supply water is fed into the tank and hot water is drawn out of the expansion chamber concurrently with opening of the faucet using a venturi aspirator. When the faucet is opened it does not control dispensing of the hot water directly but, instead, it supplies cold water at the bottom of the tank to thereby force hot water out at the top of the tank at a spout under moderate pressure.
In hot water dispenser systems the venturi aspirator jet or orifice may be in the hot water feed out of the tank or the cold water feed into the tank, each of which has advantages and disadvantages. With the aspirator in the cold water supply the venturi jet orifice inlet is fed cold supply water when the valve in the faucet is opened. As a result, a fine high velocity venturi jet is emitted from the outlet of the orifice. As is characteristic of a venturi jet, as velocity of the jet stream increases the pressure of the stream or jet in the orifice becomes negative relative to the pressure of the water to which the lateral holes of the aspirator body is exposed. In this case the lateral holes communicate with the hot water in the expansion chamber of the tank so hot water for the expansion chamber and the cold supply water fed through the orifice are projected into the main chamber of the tank to thereby force hot water out of the tank to the faucet spout. Because most of the cold supply water line pressure is dropped across the venturi, the pressure of the water in the main chamber of the tank never can reach supply line pressure. This is advantageous since it makes possible a simpler and low pressure tank design.
The problem with having the venturi in the cold water infeed to the venturi jet orifice is that in prior designs when the level of the water in the expansion tank drops to below the level of the side holes in the aspirator body, air is drawn through the tank vent line and the expansion chamber. When the aspirator injects air into the cold incoming jet stream water, the aerated water flows into the tank, causing mixing of hot and cold water which results in poor water delivery. The aerated water stream also results in air bubbles collecting in the tank, causing excessive spitting and sputtering as the water discharges from the spout of the faucet.
It will be evident that a cold side aspirator system needs a means to accomplish aspiration of water from the expansion chamber of the tank but that also prevents aspiration of air to the extent that air begins to mix with the heated water. The most usual attempt to solve the air intake problem has been to use a float device that follows the water level in the expansion chamber and blocks the aspirator body side hole when the water level drops. Using a float device is not a satisfactory solution, however, because such devices use moving parts which are vulnerable to failure due to wear and clogging by mineral deposits from the water.
In the alternatively available hot side system the cold supply line water is fed directly into the bottom region of the main chamber of the tank to pressurize the tank. In this case the pressure of the hot water in the main tank is applied to the infeed end of the venturi orifice to produce the jet and effect the negative pressure that is necessary to aspirate the hot water from the expansion chamber of the vented tank. As implied above, with the venturi in the hot side the tank must be designed to withstand water line pressure because when the faucet is operated and the valve in it is opened the cold replenishment water is fed directly from the building supply line through the valve into the tank. This increases the cost of the tank because of the high pressure withstand requirement.